Masonry and glass rained down near post-Christmas shoppers as a magnitude 4.9 earthquake rocked Christchurch on New Zealand's South Island on Sunday.

No one was injured, but at least 20 buildings in the city's center were damaged by the quake, which scientists said was the latest of hundreds of aftershocks since a 7.1 magnitude earthquake struck Christchurch on Sept. 4. That quake caused extensive damage and a handful of injuries, but no deaths.

Sunday's earthquake also came a few hours after a magnitude 7.3 earthquake struck under the sea near Vanuatu. There were no reports of damage or injuries from that quake, though it generated a small tsunami wave.

New Zealand and Vanuatu are situated on the Pacific "ring of fire" - an arc of earthquake and volcanic zones stretching from Chile in South America through Alaska and down through the South Pacific.

A powerful 7.3-magnitude earthquake struck off the western Pacific nation of Vanuatu on Sunday, triggering a small tsunami exactly six years after giant waves killed 220,000 people around the Indian Ocean.

The Hawaii-based Pacific Tsunami Warning Center said the shallow quake generated a tsunami, but it cancelled a regional warning after the wave measured only 15 centimetres (six inches) higher than normal in Vanuatu.

"Sea level readings confirm that a tsunami was generated," the centre said in its bulletin.

"This tsunami may have been destructive along coastlines of the region near the earthquake epicentre," it said, but cancelled the warning when no destructive wave hit.

The quake struck at 12:16 am on Sunday (1316 GMT Saturday), and the initial tsunami warning covered Vanuatu, Fiji and the French Pacific territory of New Caledonia. There were no reports of damage or casualties.

San Juan - A 5.4-magnitude earthquake struck the U.S. Caribbean territory on Christmas Eve, rattling windows and doors across the island but causing no major damage, officials said.

The quake occurred at a depth of 63 miles south-southwest of the capital of San Juan, according to the U.S. Geological Survey.

Blanca Saez, Ports Authority spokeswoman, told the Associated Press that the international airport is operating as usual. She said six ceiling panels fell at the American Airlines terminal, but that no one was injured.

The earthquake was centered just a couple of miles from the central mountain town of Aguas Buenas.

Emergency officials and police told local media that no damage or injuries have been reported.